Turbine meters are commonly used for large volume gas flow measurement applications where accuracy and rangeability are essential. When calibrated, properly maintained, and used in steady flow conditions, turbine meters can provide reliable and accurate fluid metering. However, at many gas metering stations flow is not steady. Pulsations from operating compressors can be present and unsteady flow can result from control valves or natural resonant lengths within the piping system. These pulsations and unsteady flow conditions can cause errors in turbine meter registration.
U.S. patent application Ser. No. 07/708,357 filed on May 31, 1991 titled "DETECTION OF ERRORS IN TURBINE METERS" and assigned to the same assignee as the present application discloses a method and apparatus for monitoring the torsional oscillation of gas turbine meters which are induced by pulsating flow. The above-referenced application discloses how these torsional oscillation can be used to predict when meter errors are likely to occur. However, there is currently no method available for quantitatively assessing the magnitude of pulsation-induced errors at field turbine metering sites. There is also no available method for correcting meter readings to compensate for such errors.
Because of the growing use of turbine meters, there is a need for a method and apparatus for quantitatively assessing and correcting turbine meter errors due to unsteady flow. Ideally, the parameters used for determining pulsation-induced errors should not involve extra measurements such as velocity modulation or differential pressures, but should result from a signal already available to the user. Heretofore, there has not been a practical field method for diagnosing, quantifying, and correcting pulsation-induced turbine meter errors.